<?php

$maxwidth = isset($_GET['maxwidth']) ? intval($_GET['maxwidth']) : null;

if (null === $maxwidth || $maxwidth === "unknown") {
    $maxwidth = 3000;
} // we need a number, so give it something unfeasable
setcookie('resolution', $maxwidth, time() + 604800, '/'); // set the cookie
// respond with an empty content
header('HTTP/1.1 204 No Content');
exit();